Gas fuels with a high concentration of hydrogen (greater than 5% by volume) require special provisions to prevent the possibility of an explosion. One such provision is to weld the fuel nozzle gas tip to the fuel nozzle body to avoid any leakage of gas through the threaded interface. While providing a leak-tight joint, the welded tips make it difficult to perform any nozzle maintenance in the field. Removing the tips necessitates sending the fuel nozzle assemblies to an off-site service shop where the nozzle tips are machined off. This becomes an expensive and time-consuming proposition for the customer.
This invention provides a simple yet effective sealing arrangement for fuel nozzles used in high-hydrogen fuel applications.
In the exemplary embodiment disclosed herein, the fuel nozzle gas tip is provided with a threaded seal ring which, after the gas tip has been threaded into engagement with the fuel nozzle body, is movable axially rearwardly to axially and radially compress a resilient metallic O-ring between the gas tip and the nozzle body. In order to prevent the seal ring on the tip from moving axially forwardly (via rotation) during use, an annular locking sleeve is provided for locking the seal ring in place. The locking sleeve comprises a cylindrical sleeve provided with a plurality of axially extending tabs at its forwardmost end, in circumferentially spaced relationship. These tabs are adapted to protrude forwardly through axial slots spaced in a similar manner about the circumference of the seal ring, when the seal ring is moved rearwardly into engagement with the nozzle body. The nozzle body itself is also provided with a plurality of circular recesses spaced circumferentially about its forward end. After the seal ring is fully engaged with the nozzle body, with the resilient metallic seal compressed therebetween, the forwardmost tabs of the locking sleeve, having been received within the circumferentially spaced axial slots the seal ring, are bent radially inwardly, and the rearward portion of the locking sleeve is staked to the circumferentially spaced recesses on the nozzle body. As a result, the locking ring is prevented from moving rotationally or axially relative to the gas tip. Furthermore, the gas tip is also prevented from rotation.
In its broadest aspects, therefore, the invention relates to a fuel nozzle for a gas turbine comprising an annular nozzle body having a forward end with interior and exterior surfaces; a gas tip having a forward fuel discharge end and a rearward mounting end, the rearward mounting end at least partially receivable in the forward end of the nozzle body; a resilient seal inserted between the nozzle body and the gas tip; a seal ring mounted on the rearward mounting end of the gas tip, adapted to axially compress the resilient seal when the seal ring is engaged with the nozzle body; and means on the exterior surface of the nozzle body for locking the seal ring to the gas tip.
The presently disclosed invention thus provides good sealing for high-hydrogen fuel gas tips while offering a design that is field maintainable. Furthermore, by using an adjustable seal ring, reliable sealing performance is achieved, regardless of variable stack-up between the gas tip and the body from assembly to assembly.
Additional objects and advantages of the present invention will become apparent from the detailed description which follows.